Radar detection circuit for a wlan transceiver

ABSTRACT

A single chip radio transceiver includes circuitry that enables detection of radar signals to enable the radio transceiver to halt communications in overlapping communication bands to avoid interference with the radar transmitting the radar pulses. The radio transceiver is operable to evaluate a number of most and second most common pulse interval values to determine whether a traditional radar signal is present. The radio transceiver also is operable to FM demodulate an incoming signal to determine whether a non-traditional radar signal, such as a bin-5 radar signal, is present. After. FM demodulation, the signal is averaged wherein a substantially large value is produced for non-traditional radar signals and a value approximately equal to zero is produced for a communication signal that is not FM modulated with a continuously increasing frequency signal. Gain control is used to limit incoming signal magnitude to a specified range of magnitudes.

CROSS REFERENCE TO RELATED PATENTS

This application claims priority to U.S. Provisional Application havinga Ser. No. of 60/844,779 and a filing date of Sep. 15, 2006, and is acontinuation-in-part of, and further claims priority to, U.S. UtilityApplication having a Ser. No. of 11/415,841 and a filing date of May 2,2006, and further claims priority to:

-   -   (1) U.S. Provisional Application having a Ser. No. of 60/502,934        and a filing date of Sep. 15, 2003,    -   (2) U.S. Utility Application having a Ser. No. of 10/815,161 and        a filing date of Mar. 31, 2004,    -   (3) U.S. Utility Application having a Ser. No. of 10/815,163 and        a filing date of Mar. 31, 2004, and    -   (4) U.S. Provisional Application having a Ser. No. of 60/735,521        and a filing date of Nov. 11, 2005,    -   all of which are expressly incorporated herein in their entirety        by reference thereto.

BACKGROUND

1. Technical Field

The present invention relates to wireless communications and, moreparticularly, wideband wireless communication systems.

2. Related Art

Communication systems are known to support wireless and wire linedcommunications between wireless and/or wire lined communication devices.Such communication systems range from national and/or internationalcellular telephone systems to the Internet to point-to-point in-homewireless networks. Each type of communication system is constructed, andhence operates, in accordance with one or more communication standards.For instance, wireless communication systems may operate in accordancewith one or more standards, including, but not limited to, IEEE 802.11,Bluetooth, advanced mobile phone services (AMPS), digital AMPS, globalsystem for mobile communications (GSM), code division multiple access(CDMA), local multi-point distribution systems (LMDS),multi-channel-multi-point distribution systems (MMDS), and/or variationsthereof.

Depending on the type of wireless communication system, a wirelesscommunication device, such as a cellular telephone, two-way radio,personal digital assistant (PDA), personal computer (PC), laptopcomputer, home entertainment equipment, etc., communicates directly orindirectly with other wireless communication devices. For directcommunications (also known as point-to-point communications), theparticipating wireless communication devices tune their receivers andtransmitters to the same channel or channels (e.g., one of a pluralityof radio frequency (RF) carriers of the wireless communication system)and communicate over that channel(s). For indirect wirelesscommunications, each wireless communication device communicates directlywith an associated base station (e.g., for cellular services) and/or anassociated access point (e.g., for an in-home or in-building wirelessnetwork) via an assigned channel. To complete a communication connectionbetween the wireless communication devices, the associated base stationsand/or associated access points communicate with each other directly,via a system controller, via a public switched telephone network (PSTN),via the Internet, and/or via some other wide area network.

Each wireless communication device includes a built-in radio transceiver(i.e., receiver and transmitter) or is coupled to an associated radiotransceiver (e.g., a station for in-home and/or in-building wirelesscommunication networks, RF modem, etc.). As is known, the transmitterincludes a data modulation stage, one or more intermediate frequencystages, and a power amplifier. The data modulation stage converts rawdata into baseband signals in accordance with the particular wirelesscommunication standard. The one or more intermediate frequency stagesmix the baseband signals with one or more local oscillations to produceRF signals. The power amplifier amplifies the RF signals prior totransmission via an antenna.

As is also known, the receiver is coupled to the antenna and includes alow noise amplifier, one or more intermediate frequency stages, afiltering stage, and a data recovery stage. The low noise amplifierreceives an inbound RF signal via the antenna and amplifies it. The oneor more intermediate frequency stages mix the amplified RF signal withone or more local oscillations to convert the amplified RF signal into abaseband signal or an intermediate frequency (IF) signal. As usedherein, the term “low IF” refers to both baseband and intermediatefrequency signals. A filtering stage filters the low IF signals toattenuate unwanted out of band signals to produce a filtered signal. Thedata recovery stage recovers raw data from the filtered signal inaccordance with the particular wireless communication standard.

One approach to using a higher intermediate frequency is to convert theRF signal to an intermediate frequency sufficiently low to allow theintegration of on-chip channel selection filters. For example, somenarrow band or low data rate systems, such as Bluetooth, use this lowintermediate frequency design approach.

Active mixers used in direct conversion radios, as well as radios thatemploy an intermediate conversion step typically comprise inputtransconductance elements, switches and an output load. These activemixers often have varying output signal characteristics due toenvironmental conditions, such as temperature, and process andmanufacturing variations. These varying output signal characteristicscan, for example, result in a mixer producing an errant localoscillation signal that affects the accuracy of an output signal'sfrequency. Having inaccurate output frequencies can result in manyundesirable outcomes, including unwanted signal filtering by adownstream filter.

Other approaches are also being pursued to achieve the design goal ofbuilding entire radios on a single chip. With all of the foregoingdesign goals, however, there is being realized an increasing need foradditional frequency bands for use by radio receivers and transmittersof all types. Along these lines, a frequency band that has heretoforebeen reserved exclusively for radar systems is being opened for use forat least some types of wireless communication systems. Among othersystems, wireless local area network (LAN) systems are being developedto take advantage of the frequency band that is being opened up whichhas been reserved for radar. One design issue, however, that accompaniesany wireless LAN device that operates in this frequency band is that ofcoexistence with radar systems. More specifically, a need exists for awireless LAN transceiver to give priority to a radar when a radaroperation is detected. Accordingly, the wireless LAN, in such ascenario, would be required to detect a radar signal within a specifiedresponse time and to communicate over a non-overlapping frequency bandthereto.

Along these lines, recent changes to government regulations will allowwireless LANs (WLANs) to share frequency spectrum with licensed radarsystems. Specifically, the frequency bands 5.25-5.35 GHz and 5.27-5.75GHz will be open in Europe, and perhaps worldwide at some point in thefuture. Since these frequency bands are shared, the wireless LANs willbe required to take a subordinate role to the licensed radar systems.This includes the incorporation of dynamic frequency selection (DFS)within the WLAN that will avoid spectrum that is occupied by a radar.What is needed, therefore, is a circuit and method for determining whena radar signal is present.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theDrawings, the Detailed Description of the Invention, and the claims.Other features and advantages of the present invention will becomeapparent from the following detailed description of the invention madewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredwith the following drawings, in which:

FIG. 1 is a functional block diagram illustrating a communication systemthat includes circuit devices and network elements and operation thereofaccording to one embodiment of the invention;

FIG. 2 is a schematic block diagram illustrating a wirelesscommunication device as a host device and an associated radio;

FIG. 3 is a schematic block diagram illustrating a wirelesscommunication device as a host device and an associated radio withmultiple input and output signal paths for generating and receivedmultiple communication signals;

FIG. 4 is a diagram that illustrates the relative difference between atraditional radar signal waveform and an 802.11 wireless LAN waveformsignal;

FIG. 5 is a diagram that illustrates two groups (blocks) of pulses of aradar signal;

FIG. 6 is a diagram that illustrates the difference in signal length forWLAN signals, traditional radar signals, and non-traditional radarsignals and is used to explain operational aspects of the variousembodiments of the present invention;

FIG. 7 is a diagram that illustrates the measurement of rise time andfall time of the pulses of the radar signal for both traditional andnon-traditional radar pulses;

FIG. 8 is a functional block diagram of a MIMO radio transceiver, andmore specifically, of a receiver portion of a radar transceiveraccording to one embodiment of the invention;

FIG. 9 is a functional block diagram of a portion of a radio transceiveraccording to one embodiment of the present invention;

FIG. 10 is a block diagram of a radar detector block for use in an802.11(a) receiver that may be within a traditional transceiver orwithin a MIMO transceiver operable to detect a traditional radar signalfor a variety of signal waveforms including traditional radar pulses and802.11(a) signals according to one embodiment of the invention;

FIG. 11 is a functional block diagram of a moving average block asemployed in one embodiment of the present invention;

FIG. 12 illustrates a threshold comparison state machine;

FIG. 13 is a flowchart that illustrates a series of steps that areperformed according to one embodiment of the invention that are used fortracking radar, especially traditional radar;

FIG. 14 is a flowchart illustrating a method for determining whether aradar signal is present according to one embodiment of the invention;

FIG. 15 is a flowchart of a method for performing radar detectionprocessing for a traditional radar signal;

FIG. 16 is a flowchart illustrating a method for performing radardetection processing for missing pulses;

FIG. 17 is a flowchart illustrating a method for performing radardetection processing for extra pulses;

FIG. 18 is a functional block diagram of one embodiment of the inventionof radar detection circuitry for detecting non-traditional radar pulses;

FIG. 19 is a flow chart that illustrates operation of a radio receiveraccording to one embodiment of the invention;

FIG. 20 is a flow chart that illustrates a method for detectingtraditional and non-traditional radar signals according to oneembodiment of the invention;

FIG. 21 is a flow chart that illustrates a method for processing pulsesas a part of determining the presence of a radar signal according to oneembodiment of the invention;

FIG. 22 is a flow chart that illustrates a method for determiningwhether a specified type of radar pulse has been detected according toone embodiment of the invention; and

FIG. 23 is a functional block diagram for a system for detectiontraditional and non-traditional radar signals according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a communication systemthat includes circuit devices and network elements and operation thereofaccording to one embodiment of the invention. More specifically, aplurality of network service areas 04, 06 and 08 are a part of a network10. Network 10 includes a plurality of base stations or access points(APs) 12-16, a plurality of wireless communication devices 18-32 and anetwork hardware component 34. The wireless communication devices 18-32may be laptop computers 18 and 26, personal digital assistants 20 and30, personal computers 24 and 32 and/or cellular telephones 22 and 28.The details of the wireless communication devices will be described ingreater detail with reference to figures described below.

The base stations or APs 12-16 are operably coupled to the networkhardware component 34 via local area network (LAN) connections 36, 38and 40. The network hardware component 34, which may be a router,switch, bridge, modem, system controller, etc., provides a wide areanetwork (WAN) connection 42 for the communication system 10 to anexternal network element such as WAN 44. Each of the base stations oraccess points 12-16 has an associated antenna or antenna array tocommunicate with the wireless communication devices in its area.Typically, the wireless communication devices 18-32 register with theparticular base station or access points 12-16 to receive services fromthe communication system 10. For direct connections (i.e.,point-to-point communications), wireless communication devicescommunicate directly via an allocated channel.

Typically, base stations are used for cellular telephone systems andlike-type systems, while access points are used for in-home orin-building wireless networks. Regardless of the particular type ofcommunication system, each wireless communication device includes abuilt-in radio and/or is coupled to a radio. Any such communicationdevice of FIG. 1 that is operable to transmit over a specified radarfrequency includes one or more embodiments of the present invention.

FIG. 2 is a functional block diagram illustrating a wirelesscommunication host device 18-32 and an associated radio 60. For cellulartelephone hosts, radio 60 is a built-in component. For personal digitalassistants hosts, laptop hosts, and/or personal computer hosts, theradio 60 may be built-in or an externally coupled component.

As illustrated, wireless communication host device 18-32 includes aprocessing module 50; a memory 52, a radio interface 54, an inputinterface 58 and an output interface 56. Processing module 50 and memory52 execute the corresponding instructions that are typically done by thehost device. For example, for a cellular telephone host device,processing module 50 performs the corresponding communication functionsin accordance with a particular cellular telephone standard.

Radio interface 54 allows data to be received from and sent to radio 60.For data received from radio 60 (e.g., inbound data), radio interface 54provides the data to processing module 50 for further processing and/orrouting to output interface 56. Output interface 56 providesconnectivity to an output device such as a display, monitor, speakers,etc., such that the received data may be displayed. Radio interface 54also provides data from processing module 50 to radio 60. Processingmodule 50 may receive the outbound data from an input device such as akeyboard, keypad, microphone, etc., via input interface 58 or generatethe data itself. For data received via input interface 58, processingmodule 50 may perform a corresponding host function on the data and/orroute it to radio 60 via radio interface 54.

Radio 60 includes a host interface 62, a digital receiver processingmodule 64, an analog-to-digital converter 66, a radar detection block67, a filtering/gain module 68, a down-conversion module 70, a low noiseamplifier 72, a receiver filter module 71, a transmitter/receiver(Tx/Rx) switch module 73, a local oscillation module 74, a memory 75, adigital transmitter processing module 76, a digital-to-analog converter78, a filtering/gain module 80, an up-conversion module 82, a poweramplifier 84, a transmitter filter module 85, and an antenna 86operatively coupled as shown. The antenna 86 is shared by the transmitand receive paths as regulated by the Tx/Rx switch module 73. Theantenna implementation will depend on the particular standard to whichthe wireless communication device is compliant.

The radar detection block 67 is operable to receive a digital lowfrequency signal (either a baseband frequency or intermediate frequencysignal in a digital form) from ADC 66 and to process such digital lowfrequency signal to determine whether a radar signal is present. In thedescribed embodiment, radar detection block 67 is operable to detectboth traditional radar pulses as well as newer non-traditional radarpulses including so called “bin 5” radar signals.

Radar detection block 67, though shown as one block, may be implementedacross several blocks including the digital transmitter processingmodule 76. Generally, radar detection block 67 represents state orcircuit level logic, computer instructions in memory that define relatedlogic, or a combination of the state or circuit level logic and computerinstructions. Generally though, radar detection block 67, upon detectinga radar signal, prompts radio 60 to inhibit communications in frequencybands that overlap with radar and, in the case of ongoingcommunications, to switch outgoing communications to a non-overlappingfrequency band (non-overlapping with radar).

Digital receiver processing module 64 and digital transmitter processingmodule 76, in combination with operational instructions stored in memory75, execute digital receiver functions and digital transmitterfunctions, respectively. The digital receiver functions include, but arenot limited to, demodulation, constellation demapping, decoding, and/ordescrambling. The digital transmitter functions include, but are notlimited to, scrambling, encoding, constellation mapping, and modulation.Digital receiver and transmitter processing modules 64 and 76,respectively, may be implemented using a shared processing device,individual processing devices, or a plurality of processing devices.Such a processing device may be a microprocessor, micro-controller,digital signal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on operationalinstructions.

Memory 75 may be a single memory device or a plurality of memorydevices. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, and/or any device that stores digital information.Note that when digital receiver processing module 64 and/or digitaltransmitter processing module 76 implements one or more of its functionsvia a state machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory storing the corresponding operational instructionsis embedded with the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Memory 75 stores,and digital receiver processing module 64 and/or digital transmitterprocessing module 76 executes operational instructions corresponding toat least some of the functions illustrated herein.

In operation, radio 60 receives outbound data 94 from wirelesscommunication host device 18-32 via host interface 62. Host interface 62routes outbound data 94 to digital transmitter processing module 76,which processes outbound data 94 in accordance with a particularwireless communication standard or protocol (e.g., IEEE 802.11(a), IEEE802.11b, Bluetooth, etc.) to produce digital transmission formatted data96. Digital transmission formatted data 96 will be a digital basebandsignal or a digital low IF signal, where the low IF typically will be inthe frequency range of one hundred kilohertz to a few megahertz.

Digital-to-analog converter 78 converts digital transmission formatteddata 96 from the digital domain to the analog domain. Filtering/gainmodule 80 filters and/or adjusts the gain of the analog baseband signalprior to providing it to up-conversion module 82. Up-conversion module82 directly converts the analog baseband signal, or low IF signal, intoan RF signal based on a transmitter local oscillation 83 provided bylocal oscillation module 74. Power amplifier 84 amplifies the RF signalto produce an outbound RF signal 98, which is filtered by transmitterfilter module 85. The antenna 86 transmits outbound RF signal 98 to atargeted device such as a base station, access point or other wirelesscommunication device.

Radio 60 also receives an inbound RF signal 88 via antenna 86, which wastransmitted by a base station, an access point, or another wirelesscommunication device. The antenna 86 provides inbound RF signal 88 toreceiver filter module 71 via Tx/Rx switch module 73, where Rx filtermodule 71 bandpass filters inbound RF signal 88. The Rx filter module 71provides the filtered RF signal to low noise amplifier 72, whichamplifies inbound RF signal 88 to produce an amplified inbound RFsignal. Low noise amplifier 72 provides the amplified inbound RF signalto down-conversion module 70, which directly converts the amplifiedinbound RF signal into an inbound low IF signal or baseband signal basedon a receiver local oscillation 81 provided by local oscillation module74. Down-conversion module 70 provides the inbound low IF signal orbaseband signal to filtering/gain module 68. Filtering/gain module 68may be implemented in accordance with the teachings of the presentinvention to filter and/or attenuate the inbound low IF signal or theinbound baseband signal to produce a filtered inbound signal.

Analog-to-digital converter 66 converts the filtered inbound signal fromthe analog domain to the digital domain to produce digital receptionformatted data 90. Digital receiver processing module 64 decodes,descrambles, demaps, and/or demodulates digital reception formatted data90 to recapture inbound data 92 in accordance with the particularwireless communication standard being implemented by radio 60. Hostinterface 62 provides the recaptured inbound data 92 to the wirelesscommunication host device 18-32 via radio interface 54.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 2 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented ona first integrated circuit, while digital receiver processing module 64,digital transmitter processing module 76 and memory 75 may beimplemented on a second integrated circuit, and the remaining componentsof radio 60, less antenna 86, may be implemented on a third integratedcircuit. As an alternate example, radio 60 may be implemented on asingle integrated circuit. As yet another example, processing module 50of the host device and digital receiver processing module 64 and digitaltransmitter processing module 76 may be a common processing deviceimplemented on a single integrated circuit.

Memory 52 and memory 75 may be implemented on a single integratedcircuit and/or on the same integrated circuit as the common processingmodules of processing module 50, digital receiver processing module 64,and digital transmitter processing module 76. As will be described, itis important that accurate oscillation signals are provided to mixersand conversion modules. A source of oscillation error is noise coupledinto oscillation circuitry through integrated circuitry biasingcircuitry. One embodiment of the present invention reduces the noise byproviding a selectable pole low pass filter in current mirror devicesformed within the one or more integrated circuits.

Local oscillation module 74 includes circuitry for adjusting an outputfrequency of a local oscillation signal provided therefrom. Localoscillation module 74 receives a frequency correction input that it usesto adjust an output local oscillation signal to produce a frequencycorrected local oscillation signal output. While local oscillationmodule 74, up-conversion module 82 and down-conversion module 70 areimplemented to perform direct conversion between baseband and RF, it isunderstood that the principles herein may also be applied readily tosystems that implement an intermediate frequency conversion step at alow intermediate frequency.

FIG. 3 is a functional block diagram illustrating a wirelesscommunication device that includes the host device 18-32 and anassociated radio 60. For cellular telephone hosts, the radio 60 is abuilt-in component. For personal digital assistants hosts, laptop hosts,and/or personal computer hosts, the radio 60 may be built-in or anexternally coupled component.

As illustrated, the host device 18-32 includes a processing module 50,memory 52, radio interface 54, input interface 58 and output interface56. The processing module 50 and memory 52 execute the correspondinginstructions that are typically done by the host device. For example,for a cellular telephone host device, the processing module 50 performsthe corresponding communication functions in accordance with aparticular cellular telephone standard.

The radio interface 54 allows data to be received from and sent to theradio 60. For data received from the radio 60 (e.g., inbound data), theradio interface 54 provides the data to the processing module 50 forfurther processing and/or routing to the output interface 56. The outputinterface 56 provides connectivity to an output display device such as adisplay, monitor, speakers, etc., such that the received data may bedisplayed. The radio interface 54 also provides data from the processingmodule 50 to the radio 60. The processing module 50 may receive theoutbound data from an input device such as a keyboard, keypad,microphone, etc., via the input interface 58 or generate the dataitself. For data received via the input interface 58, the processingmodule 50 may perform a corresponding host function on the data and/orroute it to the radio 60 via the radio interface 54.

Radio 60 includes a host interface 62, a baseband processing module 100,memory 65, a plurality of radio frequency (RF) transmitters 106-110, atransmit/receive (T/R) module 114, a plurality of antennas 81-85, aplurality of RF receivers 118-120, and a local oscillation module 74.The baseband processing module 100, in combination with operationalinstructions stored in memory 65, executes digital receiver functionsand digital transmitter functions, respectively. The digital receiverfunctions include, but are not limited to, digital intermediatefrequency to baseband conversion, demodulation, constellation demapping,decoding, de-interleaving, fast Fourier transform, cyclic prefixremoval, space and time decoding, and/or descrambling. The digitaltransmitter functions include, but are not limited to, scrambling,encoding, interleaving, constellation mapping, modulation, inverse fastFourier transform, cyclic prefix addition, space and time encoding, anddigital baseband to IF conversion. The baseband processing module 100may be implemented using one or more processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on operationalinstructions. The memory 65 may be a single memory device or a pluralityof memory devices. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, and/or any device that storesdigital information. Note that when the baseband processing module 100implements one or more of its functions via a state machine, analogcircuitry, digital circuitry, and/or logic circuitry, the memory storingthe corresponding operational instructions is embedded with thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry.

In operation, the radio 60 receives outbound data 94 from the hostdevice via the host interface 62. The baseband processing module 100receives the outbound data 94 and, based on a mode selection signal 102,produces one or more outbound symbol streams 104. The mode selectionsignal 102 will indicate a particular mode of operation that iscompliant with one or more specific modes of the various IEEE 802.11standards. For example, the mode selection signal 102 may indicate afrequency band of 2.4 GHz, a channel bandwidth of 20 or 22 MHz and amaximum bit rate of 54 megabits-per-second. In this general category,the mode selection signal will further indicate a particular rateranging from 1 megabit-per-second to 54 megabits-per-second. Inaddition, the mode selection signal will indicate a particular type ofmodulation, which includes, but is not limited to, Barker CodeModulation, BPSK, QPSK, CCK, 16 QAM and/or 64 QAM. The mode selectionsignal 102 may also include a code rate, a number of coded bits persubcarrier (NBPSC), coded bits per OFDM symbol (NCBPS), and/or data bitsper OFDM symbol (NDBPS). The mode selection signal 102 may also indicatea particular channelization for the corresponding mode that provides achannel number and corresponding center frequency. The mode selectionsignal 102 may further indicate a power spectral density mask value anda number of antennas to be initially used for a multiple input multipleoutput (MIMO) wireless communication.

The baseband processing module 100, based on the mode selection signal102 produces one or more outbound symbol streams 104 from the outbounddata 94. For example, if the mode selection signal 102 indicates that asingle transmit antenna is being utilized for the particular mode thathas been selected, the baseband processing module 100 will produce asingle outbound symbol stream 104. Alternatively, if the mode selectionsignal 102 indicates 2, 3 or 4 antennas, the baseband processing module100 will produce 2, 3 or 4 outbound symbol streams 104 from the outbounddata 94.

Depending on the number of outbound symbol streams 104 produced by thebaseband processing module 100, a corresponding number of the RFtransmitters 106-110 are enabled to convert the outbound symbol streams104 into outbound RF signals 112. In general, each of the RFtransmitters 106-110 includes a digital filter and upsampling module, adigital-to-analog conversion module, an analog filter module, afrequency up conversion module, a power amplifier, and a radio frequencybandpass filter. The RF transmitters 106-110 provide the outbound RFsignals 112 to the transmit/receive module 114, which provides eachoutbound RF signal to a corresponding antenna 81-85.

When the radio 60 is in the receive mode, the transmit/receive module114 receives one or more inbound RF signals 116 via the antennas 81-85and provides them to one or more RF receivers 118-122. The RF receiver118-122 converts the inbound RF signals 116 into a corresponding numberof inbound symbol streams 124. The number of inbound symbol streams 124will correspond to the particular mode in which the data was received.The baseband processing module 100 converts the inbound symbol streams124 into inbound data 92, which is provided to the host device 18-32 viathe host interface 62.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 3 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented ona first integrated circuit, the baseband processing module 100 andmemory 65 may be implemented on a second integrated circuit, and theremaining components of the radio 60, less the antennas 81-85, may beimplemented on a third integrated circuit. As an alternate example, theradio 60 may be implemented on a single integrated circuit. As yetanother example, the processing module 50 of the host device and thebaseband processing module 100 may be a common processing deviceimplemented on a single integrated circuit. Further, the memory 52 andmemory 65 may be implemented on a single integrated circuit and/or onthe same integrated circuit as the common processing modules ofprocessing module 50 and the baseband processing module 100. While notshown specifically in FIG. 3, it is understood that the embodiment ofFIG. 3 includes one or more radar detection blocks such as radardetection block 67 of FIG. 2 to modify or inhibit outgoing transmissionsfrom RF transmitters 106-110 for detected radar signals by one or moreof RF receivers 118-122. In one embodiment, for example, a radardetected on a radar receiver that receives ingoing communication signalsfrom a specified area or direction would result in outgoingtransmissions being inhibited that may interfere with such a signal. Inan alternate embodiment, detection of a radar on any of the receivesignal paths by any of the receivers 188-122 results in all outgoingtransmissions on a radar frequency being inhibited. In yet anotherembodiment, only outgoing transmissions having a characteristic that mayinterfere with a radar of a specified characteristic are inhibited.

FIG. 4 is a diagram that illustrates the relative difference between atraditional radar signal waveform and an 802.11 wireless LAN waveformsignal. Generally, it may be seen that radar signal pulses have asignificantly higher magnitude than the 802.11 wireless LAN waveformsignal. Additionally, radar pulses have a much shorter pulse width. Inthe example shown, each radar pulse has a 1 microsecond pulse width andis spaced apart by approximately 1 millisecond (though the figure is notto scale). The 802.11 wireless LAN waveform signal, in contrast, has aperiod that equals at least 40 microseconds and can equal 3 millisecondsin duration. Thus, the waveform of the radar pulses and the 802.11wireless LAN signal are notably different, however, which facilitatesdetection by a radar detection block operable to detect traditionalradar as disclosed herein.

Continuing to examine FIG. 4, it may be noted that the radar pulses comein blocks. While 5 pulses per block are shown, it is understood thateach block of pulses may have a different number of pulses. Generally,the radar pulses are in the 5.25-5.75 GHz frequency band having a 1 to10 MHz bandwidth. The 802.11 frequency bands that are approximate to thefrequency band of radar range from 5.15-5.35 MHz and from 5.725-5.825MHz. Accordingly, it may be seen that an overlap exists between thesetwo frequency bands for 802.11 with the frequency band for the radarpulses.

FIG. 5 is a diagram illustrating two groups (blocks) of pulses of aradar signal. Generally, it is a goal to detect a radar signal before asecond group of pulses is received. Accordingly, as may be seen for thefirst group of pulses, a radar detection block, and more particularly, astate machine of the radar detection block in conjunction with aprocessor, must be able to detect and determine that a radar signal ispresent from the five pulses shown of the first group of pulses in FIG.5. As is understood, a common characteristic of radars is that the radarantenna oscillates or rotates thereby radiating any one point in spaceonly for a limited time while the point in space is within a beam angleof the radar antenna. Accordingly, even though the radar continuouslyproduces radar pulses, they are seen by the receiver in groups and thenare not seen as the radar antenna sweeps away.

As may further be seen, a plurality of threshold levels is defined.These threshold levels are used by the state machine and the processor,in one embodiment, to determine that a traditional radar signal ispresent. The logic for concluding that a radar signal is present inrelation to the pulses will be described in greater detail below.Generally, it may be seen that the first threshold level (TH₀), in oneembodiment of the invention, is defined to be within the range of −80decibels per meter (dBm). A second threshold (TH₁) is defined at −63dBm.

The thresholds TH₀ and TH₁ are chosen in order to meet the requirementsfor radar detection sensitivity and to avoid false alarms and thus maybe modified so long as this design goal is considered for a particularradar having known signal characteristics. In a first embodiment,absolute thresholds are used. The choice of TH₀ is made by firstestimating the probability of detection and probability of false alarmfor the expected environment. In an ideal environment (known radarsignals in additive white Gaussian noise (AWGN) the computation isstraightforward. However, in practice, the thresholds will are adjustedin the described embodiments of the invention in a dynamic fashion inorder to maximize radar detection performance.

While FIG. 4 and 5 are used to illustrate the relative differencetraditional radar and an 802.11 WLAN signal, FIG. 6 illustrates thedifference in signal length for WLAN signals, traditional radar signals,and non-traditional radar signals and is used to explain operationalaspects of the various embodiments of the present invention.Specifically, it may be seen that the WLAN signal has a period thatvaries from 40 microseconds to slightly more than 3 milliseconds. Agroup of 5 traditional radar pulses are shown to approximately span a 4millisecond period. The bin 5 non-traditional radar, however, may have aperiod as long as 12 seconds. As such, the mere use of signal length todetect non-traditional radar signals may result in false detectionsbecause OFDM signals may, when combined, appear long and may triggerfalse positives.

Generally, traditional existing radar signals comprise a series of shortpulses. The new “bin 5” radar pulses, however, is more random, and cancomprise, for example either a single 12 second pulse that shows up as asingle pulse or in groups of three (4 seconds each). Thus, these bin 5and other non-traditional radar pulses can be difficult to detect. Thus,the described embodiments of the invention contemplate the use of an FMdemodulator to detect long pulses with linear FM modulation on it. Asradar effectiveness may be improved by FM modulating the radar pulse,the use of a demodulator can identify that a long pulse may be a radarsignal. Thus, we modify radar detector to detect longer pulses byincreasing a FIFO buffer size among other changes and by including an FMdemodulator to detect FM modulation. With such an arrangement, if no FMmodulation is detected, as will be explained in greater detail below,the radar detection logic is operable to conclude that nonon-traditional radar is present.

FIG. 7 is a diagram that illustrates the measurement of rise time andfall time of the pulses of the radar signal for both traditional andnon-traditional radar pulses. More specifically, a time to is defined asbeing when a rising pulse crosses the first threshold TH₀. A second timevalue t, is defined when the pulse crosses the second threshold TH₁. Athird time period is defined, t₂, as being the time when a falling pulsecrosses the TH₁ threshold. Finally, a fourth time is defined as t₃whenever the falling pulse crosses threshold TH₀. By measuring the riseand fall times, the state machine and processor executed logic, in thedescribed embodiment, may better determine whether a radar pulse wasdetected.

The logic portion performed by the processor may also be implementedwith hardware such as application specific integrated computer logic,field programmable gate array logic, etc. These crossings of TH₀ and TH₁enable a processor, state machine or other logic performing pulsedetection operations to measure a rise time, a fall time, a pulse widthand a total signal period. These measured signal characteristics make upwhat is referred herein also as pulse information that is entered withina table for evaluation to facilitate determination as to whether a radarsignal is present. In one embodiment, more than two of the values oft0-t4 are used. In an alternate embodiment, the values of t1 and t2 areused to detect a pulse length as a part of radar detection logic.

FIG. 8 is a functional block diagram of a MIMO radio transceiver, andmore specifically, of a receiver portion of a radar transceiveraccording to one embodiment of the invention. As may be seen, thetransceiver 150 includes a plurality of receive paths shown generally at154, 158 and 162. In one embodiment of the invention, transceiver 150includes only two receive paths, namely, paths 154 and 158. Each path154-162 is similar in structure to the others of paths 154-162 and itshould be understood, therefore, that a MIMO transceiver and theconcepts relating to the present invention may be applied to atransceiver having any number of receive paths similar to receive path154. Because of the similarity of the multiple receive paths, onlyreceive path 154 is described herein.

As may be seen, receive path 154 includes a receiver 166 that includesradio front end processing blocks that are operable to receive an RFsignal from an antenna and to down-convert, amplify and filter thereceived signal and then to produce an ingoing digital signal thatrepresents one of a baseband or intermediate frequency (IF) signal. Inthe described embodiment, therefore, receiver front end 166 produces alow frequency (baseband or IF) digital signal. While a single receivepath is shown as a single ended path, it should be understood that manyembodiments produce in-phase (I) and quadrature-phase (Q) signal pathsthat may be either single ended or differential for a receive signalpath.

FIG. 8 further illustrates that the described embodiment of theinvention includes a radar detection logic 170 for each receive signalpath of the MIMO transceiver. The low frequency digital signal producedby receiver 166 is then produced to radar detection logic 170 and tosignal processing block 174. Radar detection logic 170 is operable todetect the presence of either a traditional or a non-traditional radarsignal.

In the described embodiments of the invention, radar detection logic 170comprises state logic and/or circuit based logic for measure rise andfall times of a pulse, or more generally, pulse lengths that areproduced to radar signal processing logic. Generally, logic 170 includescircuitry and/or logic for detecting traditional radar signals asdescribed herein. Further, in the described embodiment, radar detectionlogic 170 includes an FM demodulator that is operable to demodulate afrequency modulated signal and, more particularly, a continuallyincreasing frequency signal to produce an indication that the receivedsignal was frequency modulated with a continually increasing frequencysignal. Thus, logic 170 is operable to detect non-traditional radarsignals as well as the traditional radar signals having short pulses. Inthe digital realm, the continually increasing signal of an FM modulatedsignal is represented by a phase ramp wherein an output of the radardetection logic indicates an FM modulated signal was received if theoutput is substantially larger than zero. A non-FM modulated signalappears substantially as noise producing a near zero or zero valueoutput. Radar signal processing logic within the signal processing blockthen evaluates the data produced by the radar detection logic 170 todetermine the presence of a radar signal including the newnon-traditional radar signal pulses such as what is known as a bin-5radar signal.

FIG. 9 is a functional block diagram of a portion of a radio transceiver200 according to one embodiment of the present invention. Initially, anRF signal received at an antenna is coupled to a low noise amplifier(LNA) 202. LNA 202 produces amplified RF to mixers 204 and 206. Mixer204 mixes the amplified RF with a local oscillation to down-convert theRF to a low frequency signal (one of a baseband frequency orintermediate frequency signal) to create a down-converted in-phase (I)channel signal. Similarly, mixer 206 mixes the received amplified RFsignal with a phase-shifted local oscillation, wherein the phase isshifted by 90°, to produce a down-converted quadrature phase (Q) channellow frequency signal. Low pass filters 208 and 210 are coupled toreceive the down-converted I and Q channel signals, respectively, toproduce filtered I and Q channel signals to a pair of variable gainamplifiers 212 and 214, respectively.

Variable gain amplifiers 212 and 214 further receive gain controlsignals from an 802.11(a) physical layer digital signal processor 216.Responsive to the gain control from processor 216, variable gainamplifiers 212 and 214 provide a corresponding amount of gain to thefiltered I and Q signals and produce amplified I and Q signals toanalog-to-digital converters 217 and 218. Analog-to-digital converters217 and 218 then convert the amplified I and Q signals to digital toproduce incoming I and Q digital signal streams to processor 216.

Radio transceiver 200 of FIG. 9 further includes a radar detection block220 that is coupled to receive the incoming I and Q digital signalstreams to detect the presence of a radar signal (traditional andnon-traditional such as bin-5). Upon detecting the presence of a radarsignal, radar detection block 220 produces control signals to processor216 to prompt processor 216 to suspend communications over frequencybands that overlap with the radar frequency bands or that may interferewith the detected radar signal.

The operation and structure of radar detection block 220 is described ingreater detail below. Generally, however, the radar detection block inthis example provides at least received signal data to enable radardetection processing logic within processor 216 to determine whether aradar signal is present. Alternatively, radar detection block 220includes logic and is operable to make the determination whether a radarsignal is present and is further operable to provide the control signalto the processor 216 to inhibit transmissions. It should be furtherunderstood that the operation of FIG. 9 illustrates operation of justone receive signal path though the teachings of FIG. 9 may readily beapplied in a MIMO transceiver to each receive signal path.

FIG. 10 is a block diagram of a radar detector block for use in an802.11(a) receiver that may be within a traditional transceiver orwithin a MIMO transceiver according to one embodiment of the invention.The 802.11(a) receiver as shown in FIG. 9 that includes radar detectionblock of FIG. 10 is a direct conversion type receiver, although theinvention is applicable to a super-heterodyne receiver as well. Bothdirect conversion and super-heterodyne topologies are commonly used for802.11 type wireless LANs.

The inputs to the radar detection block of FIG. 10 are the outputs ofthe analog-to-digital converters (ADCs) that are tapped off and producedto the radar detection circuit (as shown in FIG. 8, for example). Theinput signals produced by the ADCs are digital signals that are sampledat a sufficient rate and with a sufficient number of bits to facilitateuse for radar detection. For example, a 40 MHz sampling rate at 8 bitsof precision is adequate to detect radar systems in an 802.11(a)environment.

Radar detection block 220 of FIG. 10 is operably coupled to receive theincoming I and Q digital signal streams produced by ADC 217 and ADC 218of FIG. 9. As may be seen in FIG. 10, the incoming I and Q digitalsignal streams are received by mixers 222 and 224. Mixers 222 and 224are operatively coupled to receive each of the incoming I and Q digitalsignal streams twice to square each of the incoming I and Q digitalsignal streams. In one embodiment of the invention, the mixers areGilbert mixers that are operable to multiply the inputs (since theinputs are of approximate magnitudes). Accordingly, mixer 222 produces asquared I digital signal stream, while mixer 224 produces a squared Qdigital signal stream. The squared I and Q digital signal streams arethen produced to an adder 226 that sums the two squared signals toproduce a summed I and Q squared signal stream to a switch 228.

In a first position, the summed I and Q squared signal stream isproduced to moving average filter 230 that calculates a moving averageof the summed I and Q squared signal stream. Moving average filter 230then produces a moving average value to decibel conversion block 232,which converts the moving average value produced by filter 230 todecibel units.

Whenever switch 228 couples moving average filter 230 to adder 226, aswitch 238 couples the output of decibel conversion block 232 to athreshold comparison state machine 240. Accordingly, the moving average,in decibels, is produced to threshold comparison state machine 240 foranalysis as will be described below. Whenever switch 228 couples adder226 to a decibel conversion block 234, however, the summed I and Qsquared signal stream is produced to decibel conversion block 234 whichproduces the summed I and Q squared signal stream in decibels to asubtractor 236. Subtractor 236 is further coupled to receive andsubtract a receiver gain setting from the summed I and Q squared signalstream in decibels. The output of subtractor 236 is then coupled, byswitch 238, to threshold comparison state machine 240. Thresholdcomparison state machine 240 operates as described below to providepreliminary analysis of the detected power levels produced either bydecibel conversion block 232 or subtractor 236 to a processor 242. Radardetection logic 244 within processor 242, then analyzes the preliminaryanalysis received from threshold comparison state machine 240 todetermine whether a radar signal has been received.

This circuit of FIG. 10 computes the received power and applies eitherno filtering (option 1 in which both switches are in the low position)or a moving average filter (option 2 in which both switches are in theupper position). Option 1 is most effective for short pulse width radarswhen no interference is present. Option 2 is most effective with longerradar pulses in interference that looks random as is shown in FIG. 10.

The embodiment of FIG. 10, therefore, is a functional block diagram of aradar detection block operable to detect a traditional radar signal fora variety of signal waveforms including traditional radar pulses and802.11 based communication signals. In general, the radar detectionblock will not have prior information concerning either the radar pulsewidth or interference. Consequently, in the described embodiment, logicdrives switches 228 and 238 to the lower position (option 1) unless an802.11(a) frame is being received (as determined during call setupsignaling between an access point and a wireless host or communicationdevice in one embodiment of the invention). In the case of 802.11(a)communications, option 2 is employed (the switches are toggled to theupward position as shown) during the duration of the frame.

When option 2 is employed during a received 802.11(a) frame, thethresholds are set to be relative to the average received power. Sincethe radar signal is typically a constant envelope signal, while theinterference is more like Gaussian noise, the moving average filter willhave the effect of improving the radar signal to interference powerratio by a factor of the square root of the filter length. Theimprovement is limited by the length of the radar pulse (i.e., maximumimprovement is when the radar pulse fills the moving average filter).Thus, the threshold level and filter length are jointly selected basedon the expected radar pulses length and the detection and false alarmprobabilities.

FIG. 11 is a functional block diagram of a moving average block asemployed in one embodiment of the present invention. The moving averagefilter effectively is an integrator and can improve the radar signal tointerference level for many types of radar signals. In the describedembodiment, four delay elements 246 are included coupled in series andhaving outputs that are further produced to an adder. A summed outputfrom the adder is then produced to a divide by “N” block 248. The valueof “N” in the divide-by-N block is equal to four in the describedembodiment since there are four delay elements. The number of delayelements and the divisor “N” may each be modified according toparticular requirements.

If it is assumed that the radar signal has a constant envelope, the Iand Q components then take the form:

I(n)=A _(r)cos(ω_(r) nT+φ)

Q(n)=A _(r)sin(ω_(r) nT+φ)

where A_(r), the radar signal amplitude, and ω_(r), the down-convertedradar signal frequency, are constant (or approximately constant) duringthe radar pulse. The radar signal is zero outside of the received pulse.In contrast, the received. 802.11(a) signal can be modeled as twoGaussian signals:

I(n)=G _(i)(n)

Q(n)=G _(q)(n)

The moving average filter of length n computes the following:

$y = {{\sum\limits_{i = 1}^{k}I_{i}^{2}} + Q_{i}^{2}}$

With an input signal that is composed of a radar signal embedded withinan 802.11(a) frame, the output of the moving average filter is:

I(n) = A_(r)cos (ϖ_(r)nT + ϕ) + G_(i)(n)Q(n) = A_(r)sin (ϖ_(r)nT + ϕ) + G_(q)(n)$y = {{\sum\limits_{i = 1}^{k}{A_{r}^{2}\left( {{\cos^{2}\left( {{\varpi_{r}{iT}} + \phi} \right)} + {\sin^{2}\left( {{\varpi_{r}{iT}} + \phi} \right)}} \right)}} + {A_{r}{\cos \left( {{\varpi_{r}{iT}} + \phi} \right)}{G_{i}(i)}} + {G_{i}^{2}(i)} + {A_{r}{\sin \left( {{\varpi_{r}{iT}} + \phi} \right)}{G_{q}(i)}} + {G_{q}^{2}(i)}}$$y = {{kA}_{r}^{2} + {\sum\limits_{i = 1}^{k}{A_{r}{\cos \left( {{\varpi_{r}{iT}} + \phi} \right)}{G_{i}(i)}}} + {G_{i}^{2}(i)} + {A_{r}{\sin \left( {{\varpi_{r}{iT}} + \phi} \right)}{G_{q}(i)}} + {G_{q}^{2}(i)}}$

With the radar and signal model given above, y has a non-centralchi-square distribution with 2k degrees of freedom. Thus, the relativeerror in the measurement of y is given by:

$\begin{matrix}{{{Relative}\mspace{14mu} {Error}} = {\left( {{standard}\mspace{14mu} {deviation}\mspace{14mu} {of}\mspace{14mu} y} \right)/\left( {{mean}\mspace{14mu} {of}\mspace{14mu} y} \right)}} \\{= \frac{\sigma_{y}}{m_{y}}} \\{= \frac{\sqrt{{4k\; \sigma_{wlan}^{4}} + {4k\; A_{r}^{2}\sigma_{wlan}^{2}}}}{{2k\; \sigma_{wlan}^{2}} + {k\; A_{r}^{2}}}}\end{matrix}$

which decreases by a factor of the square root of k with increasing k.

FIG. 12 illustrates a threshold comparison state machine. This devicemeasures the time instants when the radar pulse crosses two thresholds.The output takes the form of 4 time measurements: start time (T₀), risetime (T₁), pulse width (T₂), and fall time (T₃). A set of the 4 timemeasurements is recorded for every complete cycle back to start.

The state machine operates as follows. It originates in the start stateand observes the incoming power estimate P. When P exceeds threshold P₀,the start time (T₀) is recorded and the state is advanced to Rising0.Once in Rising0, a counter is initiated to record the total time in thatstate (T₁). If the incoming power estimate drops below P₀, then thestate machine is reset and it returns to Start.

When P exceeds the second threshold, P₁, the state machine advances tostate Rising1. The time it spends in this state is recorded in T2. WhenP drops below P₁, the state machine advances to Falling0. The time inthis state is recorded in T₃. If, while in the Falling0 state, P risesback up to P₁, then the state machine returns to the Rising1 state. T₂is then incremented by the contents of T₃ and T₃ is reset. This processof moving back and forth between the Rising1 and Falling0 states canhappen multiple times. After P drops below P₀, the state machine returnsto Start and the complete set of 4 time measurements are forwarded tothe processor.

The final radar detection decision is made by a programmable processoras shown in the embodiment of FIG. 8. In the embodiment of FIG. 9,however, the final radar detection decision may be made either in theprocessor or in radar detection block 220. Referring again to FIG. 10,processor 242, and more particularly, radar detection logic 244,periodically reviews the pulse data collected by the state machine 240,and compares it with the characteristics of known traditional radarsignals. One key characteristic for determining radar presence, however,is the pulse repetition frequency. Thus, the processor is operable tomatch multiple received pulses with the same relative spacing. When asequence of this type is observed, detection is declared. Otherwise, thepulse data is discarded, and the processor waits for new data. Thismulti-layer approach helps minimize false detections of traditionalradar signals while maximizing the chances that actual radars aredetected. In the described embodiment of the invention, a processorreceives the output of the state machine and logic defined therein (inradar detection block 244 of FIG. 10, for example) analyzes the outputof the state machine to determine whether a radar signal has beenreceived. It should be understood that the following logic, as definedin block 244 and executed by processor 242, may readily be formed inhardware as described before.

FIG. 13 is a flowchart that illustrates a series of steps that areperformed according to one embodiment of the invention that are used fortracking radar, especially traditional radar. Generally, the inventionincludes measuring signal characteristics to determine if a receivedsignal has a characteristic of a radar pulse and to further determinewhether a pattern of pulses is consistent with a radar pattern. Morespecifically, the invention includes determining whether a receivedsignal has exceeded a first threshold (step 250) and, when the firstthreshold is exceeded, a timer is initiated to track or measure a risetime (step 252). The time is turned off and the rise time is determinedwhen the rising signal crosses a second threshold. Thus, the inventionincludes determining that the received signal has crossed (the secondthreshold (step 254).

The embodiment of the invention further includes determining a pulsewidth. Thus, once the second threshold has been reached, the inventionincludes initiating a second timer to measure an amount of time abovethe second threshold (and therefore the pulse width) (step 256). Theembodiment of the invention further includes determining a receivedsignal has fallen below the second threshold (step 258). The differencein time between the two crossings of the second threshold define thepulse width of a received signal. If the second timer is initialized tostart counting from zero, the value of the second timer represents thepulse width. In one embodiment, this pulse width is a key characteristicin determining whether a traditional radar signal has been receivedthough, in an alternate embodiment, may also be used for determiningwhether a non-traditional radar has been received.

Once the second threshold is crossed in a downward position, meaning thereceived signal levels has crossed from above to below the secondthreshold, a third timer is initialized to track a fall time (step 260).Once the signal crosses the first threshold in the downward direction,the third timer is stopped and the fall time is determined (step 262),which fall is the time required for the signal level to fall from thesecond to the first threshold. Accordingly, the invention furtherincludes producing first, second and third timer values to logic fordetermining whether a radar pulse has been received (step 264). Finally,if a radar pulse has been received, the method of the embodiment of theinvention includes stopping all transmissions in frequency bands thatoverlap with radar frequency bands (step 266).

FIG. 14 is a flowchart illustrating a method for determining whether aradar signal is present according to one embodiment of the invention.For the described embodiment, it is assumed hardware of a radio receiveris continually filling a first in/first out (FIFO) with the pulseinformation. Moreover, in the described embodiment of the invention, theinventive method is repeated at periodic intervals of less than onesecond.

Initially, the invention includes receiving and detecting incomingpulses and placing the pulse information in a FIFO register to detect atraditional radar signal presence (step 270). Detecting the incomingpulses includes measuring pulse characteristics such as rise time, pulsewidth and fall time. Thereafter, the invention includes producing pulseinformation to a processor and clearing the FIFO (step 272). Generally,this step includes loading pulse data (pulse information) into theprogrammable processor (in the described embodiment) or other logic. Inone embodiment, the pulse data is loaded by direct transfer such as bydirect memory access (DMA).

After the pulse data is loaded, a table of pulse data is generated for aseries of pulses (step 274). If the total number of pulses is less thana specified number, processing is suspended (stopped) until thespecified number of pulses is listed within the table (step 276). Inaddition to adding pulse data to the table, the embodiment of theinvention includes removing pulse information from the generated tablefor any pulse having a pulse width less than a specified minimum widthamount and greater than a specified maximum width amount (step 278). Inan alternate embodiment, pulse data is only placed within the table forfurther analysis if the pulse width is within a specified range for agiven pulse. Accordingly, for this embodiment, the step of removingpulse data for such a pulse is unnecessary. In either embodiment,however, pulses that are either too long or too short to be a radarpulse are removed from the table of pulse data entries. Typical radarsystems have pulses with a pulse width in the range of one to threemicroseconds.

The embodiment of the invention further includes determining whether atotal number of pulses is less than a specified number and, if so, stopsfurther processing until the table has pulse data for a specified numberof pulses (step 280). In one embodiment of the invention, the specifiednumber is equal to six. Thereafter, the invention includes grouping aplurality of pulse data entries to enable detection of a specified radarpulse (step 282).

In the described embodiment, the group of pulses are grouped by time.More specifically, a nominal value of 210 milliseconds is used to grouppulses. In the very specific embodiment, such a grouping is referred toas an epoch. The epoch or group length is set to be long enough toperform radar detection processing (step 284) and to cover the burstlengths sufficiently long to detect desired radar systems. This steptakes advantage of a radar characteristic of radar systems of pulsesbeing transmitted and arriving in bursts. Although it is not knownexactly how long the bursts will be for a radar, the nominal value of210 milliseconds should be adequately long to facilitate identifying areceived radar signal. Finally, if a radar pulse has been received, theinvention includes inhibiting or stopping transmission in frequencybands that overlap with radar frequency bands (step 286).

FIG. 15 is a flowchart of a method for performing radar detectionprocessing for a traditional radar signal. In some cases, it is expectedthat a valid radar signal may not be detected due to interference withone or more pulses. Accordingly, the group of pulses for which no radarwas detected is evaluated for a missing pulse. Thus, for the groupedplurality of pulse information entries (epoch), the invention includesgenerating a first list of pulse repetition intervals by subtracting astart time for a given pulse from a start time for an immediatelypreceding pulse for each pulse in the group (step 290). It isunderstood, of course, that this step cannot be performed for the firstpulse.

Thereafter, the invention includes quantizing pulse repetition intervalswith a specified granularity (step 292). Generally, received pulse datahas a degree of resolution that is not necessary and may result in falsedeterminations regarding radar detection conclusions. In one embodimentof the invention, the data is quantized to a resolution of 25milliseconds and a smallest incremental value. Thereafter, the inventionincludes removing all pulses not having a pulse repetition intervalvalue within a specified range (step 294). If the total number of pulsesis less than a specified number (six in the described embodiment) theprocess is stopped and is repeated for a subsequent grouped plurality ofpulse information entries (step 296).

Once a group of pulses (epoch in the described embodiment) contains agroup of pulses that is equal to or exceeds the specified number ofrequired pulses (six in the described embodiment), the inventionincludes determining (by counting) which pulses have the most common andsecond most common pulse interval values in the group of pulseinformation entries (step 298). The method further includes determiningif a total number of most common pulse interval values is greater thanor equal to the specified number and therefore determining that a radarpulse has been detected (step 300). If the pulse train (group of pulses)does not suggest radar presence, the invention includes examining thepulse train to determine if the pulse train is missing a radar pulse(step 302). The specific steps for determining that a radar is presentnotwithstanding a missing pulse is illustrated in relation to FIG. 16.

If analysis of the pulse train for missing radar pulses does not suggestradar presence, the invention includes examining the pulse train todetermine if the pulse train includes an extra radar pulse (step 304).If a radar pulse is detected in any one of the prior steps, theinvention further includes suspending transmission in overlappingfrequency bands and classify radar by comparing frequency of pulses fromfirst list of pulse repetition intervals to known radar signals (step306). Finally, the invention includes continuing monitoring for radarand, once a radar signal is determined to not be present, resumingtransmission of communication signals in overlapping frequency bands(radar bands) (step 308).

FIG. 15 illustrated a method for determining whether a radar signal ispresent and whether transmissions in overlapping frequency bands shouldbe suspended. Within the steps of FIG. 15, there are two steps fordetermining whether a radar is present even if a pulse is missing (forexample, due to interference) or if there is an extra pulse (forexample, due to spurious noise or other noise source) in steps 304 and306, respectively. Each of these two steps, however, further includes aseries of steps for determining the same.

FIG. 16 is a flowchart that illustrated a method for performing radardetection processing for missing pulses according to one embodiment.Referring now to FIG. 16, the method includes evaluating whether a2*pulse interval of a most common pulse interval value is equal to apulse interval of a second most common pulse interval value (step 310).

Additionally, the invention includes evaluating whether the 2*pulseinterval of the second most common pulse interval value is equal to thepulse interval of the most common pulse interval value (step 312). Also,the invention includes determining if the total number of most commonand second most common pulses is greater than the specified number (step314). Finally, the invention includes determining that a radar pulse ispresent if any of the above three steps are true (step 316). Generally,if any of these steps yields a true result, then a radar is present anddetectable even if interference prevents receipt of a radar pulse.

FIG. 17 is a flowchart illustrating a method for performing radardetection processing for extra pulses according to one embodiment. Atype of interference that may interfere with radar detection fortraditional radars is the introduction of a signal that appears to be apulse. Thus, referring now to FIG. 17, an embodiment of an inventivemethod includes performing analysis for determining a radar signal ispresent even in the presence of an extra signal appearing as a pulse.More specifically, the invention includes for a grouped plurality ofpulse data entries, generating a second list of pulse repetitionintervals by subtracting a start time for a given pulse from a starttime for a pulse preceding an immediately preceding pulse (step 318).Thereafter, the pulse repetition intervals are quantized with aspecified granularity (step 320). The invention further includesremoving all pulses not having a pulse repetition interval value withina specified range (step 322). The remaining pulse intervals of a firstlist of pulse repetition intervals are then compared to the second listof pulse repetition intervals (step 324). Finally, the inventionincludes evaluating whether if pulse periods match from the comparison,and if the total number of pulses in the second list of pulse repetitionintervals is greater than a specified number, determining whether aradar is present (step 326).

In an alternate embodiment of the invention, an FM demodulator is usedin a radar detection circuit. The FM demodulator is particularly helpfulin detecting so called “Bin 5” radars which are less predictable andhave longer lengths than other forms of radar. In yet anotherembodiment, a combination of the various radar circuits disclosed hereinare jointly employed to maximize the detection of radar signals. BothFIG. 16 and 17 relate, generally, to traditional radar signals.

FIG. 18 is a functional block diagram of one embodiment of the inventionof radar detection circuitry for detecting non-traditional radar pulses.Generally, the non-traditional radar pulse is characterized by arelatively long period as discussed in relation to FIG. 6 above. Atraditional approach for detecting a radar pulse including measuringpulse lengths by detecting crossings of specified threshold signalstrength/magnitudes (e.g., time between t1 and t2 of FIG. 7) could beused to detect a non-traditional radar pulse having a long period (e.g.,100 micro-seconds or more). It is possible, however, that a falsepositive could result from an orthogonal frequency division multiplexing(OFDM) signal especially if, for some reason, the receiver is not awarethat an OFDM signal is being received. Thus, it is possible that thereceiver will not accurately distinguish between an OFDM ornon-traditional radar signal by merely analyzing a received signal for along pulse.

If an OFDM signal is processed by an FM demodulator, however, the outputappears as random noise. A non-traditional radar signal (e.g., bin-5radar) that is processed by an FM demodulator, however, produces alinear ramp as an output because frequency increases at a constant ratefor the non-traditional radar signal. Typically, the radar pulseinitially is characterized by a low frequency offset and increases infrequency at a constant rate over course of pulse. Thus, a rudimentaryFM demodulator may be used to detect the non-traditional radar. Byaveraging the signal, the output of the FM demodulator will besubstantially equal to zero without a signal that continually increasesin frequency to produce a phase ramp in the digital realm. For a signalthat generates a digital phase ramp, however, averaging the signal stillresults in an output having a substantially large output value to enablethe receiver to determine that radar was received.

More specifically, a linear frequency modulated signal has the form:

y(t) = ^(j2π(f₀t + φ(t)))${\varphi \left( t_{0} \right)} = {{\int_{0}^{t_{0}}{k\; t{t}}} = \frac{k\; t_{0}^{2}}{2}}$

-   -   wherein K is the modulation in Hz/second, and f0 is the carrier        frequency in Hz. For a received signal y(t), K can be found by        multiplying the conjugate of derivative of y(t):

$\begin{matrix}{{{y(t)}\left( {j\left( \frac{y}{t} \right)}^{*} \right)} = {{^{{j2\pi}{({{f_{0}t} + {\varphi {(t)}}})}}(j)}\left( {\frac{}{t}{{j2\pi}\left( {{f_{0}t} + {\varphi (t)}} \right)}} \right)^{*}^{- {{j2\pi}{({{f_{0}t} + {\varphi {(t)}}})}}}}} \\{= {2{\pi \left( {f_{0} + \frac{{\varphi (t)}}{t}} \right)}}} \\{= {2{\pi \left( {f_{0} + {k\; t}} \right)}}}\end{matrix}$

For a real value of k, the expression may be written as:

y(t) = i(t) + j q(t)${{Re}\left\lbrack {{y(t)}\left( {j\frac{y}{t}} \right)} \right\rbrack} = {{{i(t)}\frac{{q(t)}}{t}} - {{q(t)}\frac{{i(t)}}{t}}}$

In a sampled system, the differential signals may be expressed as:

$\begin{matrix}{{{Re}\left\lbrack {{y(n)}\left( {j\frac{{y(n)}}{t}} \right)} \right\rbrack} \approx {{{i(n)}\frac{{q(n)} - {q\left( {n - 1} \right)}}{\Delta \; t}} - {{q(n)}\frac{{i(n)} - {i\left( {n - 1} \right)}}{\Delta \; t}}}} \\{= {\frac{1}{\Delta \; t}\left\lbrack {{{q(n)}{i\left( {n - 1} \right)}} - {{i(n)}{q\left( {n - 1} \right)}}} \right\rbrack}}\end{matrix}$

The expression for the real part of the signal, therefore, may beimplemented with an architecture shown in FIG. 18. Thus, a radioreceiver 350 includes baseband filtering circuitry 352 that produces astream of digital in-phase and quadrature phase signals (I_(N) andQ_(N)) that are produced to two circuit blocks that operate in aparallel manner. Specifically, the digital signals on the I and Qbranches are produced to I and Q path shift registers 368 and 370,respectively, to provide a gain adjustment by way of right shifts to theFM demodulator that is operably coupled downstream of the shiftregisters. The digital signals on the I and Q branches are also producedto a block that is operable to measure a power level of the receivedsignal.

Specifically, the signals on the I and Q branches are produced to a pairof inputs for each of a pair of multipliers 354 and 356 which produce asquare of each signal to a summing block 358. The output of the summingblock is therefore a sum of the I and Q signals squared. The output ofsumming block 358 is then produced to a moving average filter 360 thatproduces a moving average for a specified number of samples to a LOG₂block 362. The output of block 362 is then produced to a summing block364 that is operable to subtract a specified offset value. The output ofthe summing block 364 is then produced to the shift registers 368 and370 that provide necessary gain adjustments to scale a signal to amanageable value for downstream circuitry.

Threshold compare block 366 is operably coupled to receive the output ofsumming block 358 as well and produces threshold crossing values to adownstream processor or radar detection logic that measures pulselengths. Effectively, a threshold crossing as detected by thresholdcompare block 366 is a start time of a signal and initiates a counter tocount the duration of the signal.

In relation to a similar structure described previously for detectingtraditional radar pulses, the downstream radar detection logic defines alarger FIFO buffer in one embodiment for storing the outputs ofthreshold compare block 366 to determine pulse lengths in relation to aFIFO buffer used for storing threshold values used only for detectingtraditional radar signals. The reason a larger FIFO buffer is used inone embodiment is that the longer pulse widths of the non-traditionalradar signals required a larger FIFO for adequate resolution.

Referring back to FIG. 18, the in-phase and quadrature-phase outputs ofthe shift registers 368 and 370 are produced to delay elements 372 and374, respectively, and to cross-coupled multipliers 378 and 376,respectively. Cross-coupled multipliers 376 and 378 are also coupled toreceive a delayed output of delay elements 372 and 374, respectively. Assuch, multiplier 376 receives q(n) and i(n-1) to produces q(n)*i(n-1).Multiplier 378 receives i(n) and q(n-1) to produce i(n)*q(n-1). Theoutput of summing block 380, which is operable to invert the sign of theoutput of multiplier 378, is equal to q(n)*i(n-1)-i(n)*q(n-1), whichoutput is defined above in equation (9). The output is then averagedover a specified number of samples (approximately 30 in the describedembodiment) by moving average block 382. The values going out of summingblock 380 and into moving average block 382 reflect an instantaneousfrequency. Thus, moving average block 382 produces an average ofinstantaneous frequency in the described embodiment of the invention. Itshould be understood that any type of filter may be used. The describedembodiment includes a moving average filter because of its simplicityand low cost. Generally, any type of smoothing and averaging functionmay be utilized. Generally, an OFDM signal results in an average signalmagnitude value of zero or a very small number near zero. Thus, movingaverage block 382 is operable to reduce erroneous conclusions based upona signal spike or an increased noise signal. The outputs of movingaverage block 382 are then produced to a FIFO buffer. In the describedembodiment, the FIFO buffer is located in a physical layer but the radardetection logic exists in an upper layer that is operable to evaluatethe contents of the FIFO and the duration of the pulse by evaluating theoutput of threshold compare block 366 to determine whether a bin-5 typeradar is present. Finally, it should be understood that, in thedescribed embodiment, there exists one FIFO buffer for each antenna of amulti-antenna receiver.

FIG. 19 is a flow chart that illustrates operation of a radio receiveraccording to one embodiment of the invention. The method includesinitially producing I and Q digital waveform signals from a basebandfiltering block (step 400). Thereafter, the method includes producing again control signal and adjusting a gain of a signal that is to be FMdemodulated (step 402). The step of producing a gain control signalincludes, in one embodiment, squaring each of the in-phase andquadrature-phase signals and summing the squared signals, filtering togenerate a moving average of the sum, taking a log of the moving averagevalue and subtracting an offset. A shift register then performs a rightshift based upon the gain control signal. Other methods for generating again control signal may be used. Generally, however, a desired result isto reduce or increase a gain of a signal produced to an FM demodulatorto produce a signal to the FM demodulator having a magnitude within aspecified range defined at least in part by capabilities of downstreamcomponents.

The subsequent step is to FM demodulate in-phase and quadrature-phasedigital waveform signals (step 404). In the described embodiment, asimple demodulator is used that primarily provides an output thatreflects whether an input signal was FM modulated. As described before,an FM modulated signal produces a phase ramp in the digital domain whichphase ramp may be used to identify the presence of a frequency modulatedradar. The FM demodulated signal is then averaged (step 406) andevaluated to determine the presence of a non-traditional radar signal(step 408).

FIG. 20 is a flow chart that illustrates a method for detectingtraditional and non-traditional radar signals according to oneembodiment of the invention. The method includes, for at least one of aplurality of receive signal paths, receiving a traditional radar signal(step 420). Thereafter, the method includes performing traditional radarsignal processing and detecting the presence of the traditional radarsignal (step 422). In addition, the method includes for at least one ofa plurality of receive signal paths, receiving a non-traditional signal(step 424). The method also includes FM demodulating the non-traditionalradar signal and averaging the FM demodulated non-traditional radarsignal (step 426). Finally, the method includes evaluating the averagedFM demodulated signal to determine presence of a non-traditional radarsignal (step 428). It should be understood that the method of FIG. 20 isa high level description of the method and that other described stepsmay be included as well.

FIG. 21 is a method according to one embodiment of the invention forgetting pulse data into one group for processing as a part ofdetermining whether a non-traditional radar with long pulses is beingdetected. Generally, one aspect of the method of FIG. 21 includesdetermining if pulse start times are triggered due to nulls and otherinterference that might reset a start time while a long radar pulse isbeing received. For example, if a threshold detector detects a thresholdcrossing and indicates a start time at the beginning of a long radarpulse, a null may cause the start timer to reset. Since long radarpulses are determined in part by the length of the pulse, such a nullmay result in the long radar pulse not being detected. As such, FIG. 21illustrates a method for eliminating a subsequent start time todetermine that two shorter pulses actually were part of one longerpulse.

Specifically, the method includes reading pulse information from eachreceive path FIFO buffer (currently 2 FIFO buffers in the describedembodiment) into groups of arrays (step 500). Each group contains astart time array, a pulse width array, and an FM value array and may beseen as an array of the form:

(Start_time_0, Pulse_width0, FM_0) (Start_time_1, Pulse_witdth_1, FM_1)... (Start_time_n, Pulse_width_n, FM_n)

The method also includes combining adjacent pulses in each array (step502). If the difference in start times between two adjacent pulses isless than a minimum spacing value (MIN_SPACING in the describedembodiment), the method includes deleting the second pulse and settingthe pulse width for the first pulse equal to the combined pulse width ofthe two original pulse widths and setting an FM value equal to the sumof the two originally determined FM values. Thus, when receiving anon-traditional radar pulse, receiver operation may result in a nullbeing generated in the middle of a non-traditional pulse being received.This will prevent the pulse from appearing as two separate pulses. Whenthe spacing value are less than a specified value, the radar detector isoperable to determine that a null or other operational anomaly occurredthereby driving the conclusion that the two pulses are actually just onepulse and should be combined. Finally, the method of step 502 includesrepeating the process for all pulses in each array.

Thereafter, the method includes combining all groups (in the describedembodiment, at least two groups) into one group (step 504).

The new group is then sorted according to start time (step 506).Adjacent pulses are combined together again as described above, but ifthe start times between two adjacent pulses are less than the specifiedminimum spacing (e.g., MIN_SPACING in the described embodiment), the 2ndpulse is deleted and the 1st pulse is kept but the pulse widths and FMvalues are not combined or added. FIG. 21 thus presents a method for afirst part of a two-part process for determining whether a long radarpulse has been detected. Generally, FIG. 21 illustrates a preliminarydata manipulation stage to prepare pulse data for an analysis that willthen, in a second part of a two-part process, determine whether anon-traditional long radar pulse exists.

FIG. 22 is a flow chart that illustrates one embodiment for determiningwhether a non-traditional radar has been detected. Generally, an FMdemodulator is used to detect the presence of non-traditional radarsignals such as “Bin-5” radar signals that typically have a much longerpulse width than traditional radar signals. Because OFDM transmissionscould appear as very long period signals thereby generating falsetriggers if mere pulse width is used to identify non-traditional radarsignals, the embodiments of the invention include using an FMdemodulator to detect a non-traditional radar signal since an OFDMsignal would appear as noise to the FM demodulator. Thus, determining anFM value helps distinguish real FM radar pulses from 802.11 frames thatmay falsely trigger a radar detection.

Thus, the embodiment includes adding pulse start times to the long pulsebuffer that meet the criteria: the determined pulse width is between aspecified minimum pulse width (MIN_WIDTH in one embodiment) and amaximum pulse width (MAX_WIDTH in one embodiment) (step 510).

A pulse is potentially a radar pulse if an FM detected pulse width isgreater than a specified pulse width value and is generally determinedby the formula FM>MIN_FM where “FM” represents the absolute value of thedifference of the estimate of the frequency at the start of the pulseand the estimate of the frequency at the end of the pulse as determinedby the FM demodulator. Stated differently, a positive value for “FM”reflects a continuously increasing frequency which is detected by an FMdemodulator to generate a continuously increasing output of a filtersuch as moving average block 382.

If the difference in start time between the newest pulse in the longpulse buffer and the oldest pulse is greater than a specified value (avariable identified as MAX_WINDOW in one embodiment of the invention),the oldest pulse is removed. This process is repeated until no morepulses are removed (step 512). In one embodiment, this specified valueis 8 seconds.

If more than a specified number of long pulses detected by the FMdemodulator (a variable named N_LONG_PULSES is used in one embodiment)remain in the long pulse buffer, a radar detection is declared (step514). In the described embodiment, the long pulse buffer is implementedas a sliding window having, typically, an 8 second window length orperiod. Thus, when a specified number of pulses are detected andrecorded in this long pulse buffer (sliding window), a radar signal(non-traditional radar) is determined to be detected and declared toinhibit conflicting transmissions. If no radar detection is declared,the pulse record is used to perform the short pulse radar detection fortraditional radar pulses (step 516) as described in earlier relation toearlier figures.

FIG. 23 is a functional block diagram for a system for detectiontraditional and non-traditional radar signals according to oneembodiment of the invention. Generally, the circuitry of FIG. 23 isoperable to FM demodulate a received signal, manipulate and analyze longpulse data to determine if a non-traditional radar presence exists and,if not, to determine whether a traditional radar signal exists. Thesystem includes, therefore, receiving FM values for instantaneousfrequency values into a moving average filter. The FM values may begenerated by FM demodulation circuitry, as shown in relation to FIG. 18,and is received by a filter which, here, is moving average filter 382.The outputs of the FM demodulation logic or circuitry is then producedto a filter which, in the described embodiment, comprises filter 382. Afiltered value produced by filter 382 indicates the presence of a phaseramp which, in the frequency domain, reflects a frequency modulatedsignal with a continuously increasing frequency. The output of filter382 is then produced to a long pulse FIFO 600 which stores pulse datafor received pulses. Specifically, FIFO 600 is operably disposed toreceive FM values from filter 382 as well as pulse start times and pulsewidths as determined from logic such as that shown in relation to FIG.18. In the described embodiment, FIFO 600 is formed at the physicallayer. A radar processing block 604 then processes and analyzes the datalong pulse FIFO 600 to determine the presence of a non-traditionalradar. In the described embodiment of the invention, radar processingblock 604 is implemented in an upper medium access control (MAC) layer.

In a first part of radar detection logic 608, pulse data is manipulatedto eliminate the effects of nulls and other anomalies during thepresence and detection of a non-traditional long pulse radar. The methodis similar to that described in relation to FIG. 18. The manipulateddata is then evaluated in a second part of radar detection logic 612 todetermine whether a non-traditional radar has been detected. The methodis similar to that described in portions of FIG. 18 and FIG. 19.Finally, if logic 612 determines that a non-traditional radar has notbeen detected, the method includes determining in a third part of radardetection logic 616 whether a traditional radar signal is present asdescribed in relation to FIGS. 4-17.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and detailed description. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but, on the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the claims. Any aspectshown in any of the embodiments of the described invention, may, forexample, be combined with aspects of other embodiments for yet anotherembodiment of the present invention. As may be seen, the describedembodiments may be modified in many different ways without departingfrom the scope or teachings of the invention.

1. A method in wireless communication transceiver for detecting radar,comprising: reading pulse information from each receive path first infirst out buffer (FIFO) into groups of arrays, wherein each group ofarrays includes a start time array, a pulse width array, and an FM valuearray wherein the FM values represent an absolute value of a differencean estimate of a frequency at a start of the pulse and an estimate of afrequency at an end of the pulse as determined by an FM demodulator;combining adjacent pulses in each array wherein, if the difference instart times between two adjacent pulses is less than a specified minimumspacing value, the method includes deleting the 2nd pulse and settingthe pulse width for the first pulse equal to the combined pulse width ofthe two original pulse widths; and setting an FM value equal to the sumof the FM values of the two adjacent pulse widths.
 2. The method ofclaim 1 wherein the process is repeated for all pulses in the arrays ofpulse information.
 3. The method of claim 2 wherein the method isperformed for each FIFO for each antenna.
 4. The method of claim 1further including combining each group of arrays into a single group. 5.The method of claim 4 further including sorting the pulses within thesingle group according to start time.
 6. The method of claim 5 furtherincluding combining pulses again and, if the start time between twoadjacent pulses is less than a minimum spacing value, deleting thesecond pulse and keeping the first pulse without adding the pulsewidths.
 7. The method of claim 6 further including repeating the step ofdeleting the second pulse and keeping the first pulse without adding thepulse widths until no more pulses may be deleted.
 8. The method of claim7 further including determining whether a remaining number of pulsesexceeds a specified value to determine that a long non-traditional radarhas been detected.
 9. The method of claim 7 further includingdetermining whether a remaining number of pulses does not exceed aspecified value to determine that a long non-traditional radar has notbeen detected.
 10. The method of claim 9 further including performingtraditional radar analysis to determine a traditional radar signal ispresent.
 11. A method for detecting a radar signal, comprising: addingpulse start times to a long pulse buffer for each pulse having a pulsewidth that is greater than a minimum width value and less than a maximumwidth value; if a difference in start times between the newest pulse inthe long pulse buffer and the oldest pulse is greater than a maximumwindow value, removing the oldest pulse; repeating previous step untilno more pulses are removed; and if a number of pulses greater than aspecified number of long pulses remain in the long pulse buffer,determining that a radar has been detected.
 12. The method of claim 11further including, if a radar signal is not detected because the numberof pulses was not greater than the specified number of long pulses,performing radar pulse detection for traditional radar signals.
 13. Themethod of claim 11 wherein the method is operable to detect non-standardradar pulses having non-traditional long pulse lengths.
 14. The methodof claim 11 wherein the method is operable to detect bin-5 categoryradar signals.
 15. An integrated circuit radio transceiver, comprising:circuitry and logic for detecting traditional short pulse radar signals;circuitry and logic for detecting non-traditional long pulse radarsignals; circuitry and logic for inhibiting wireless transmissions upondetection of either a short pulse or a long pulse radar signal; andwherein the circuitry and logic for detecting the non-traditional longpulse radar signals comprises logic for: reading pulse information fromeach receive path first in first out buffer (FIFO) (currently 2) intogroups of arrays, wherein each group of arrays includes a start timearray, a pulse width array, and an FM value array; combining adjacentpulses in each array wherein, if the difference in start times betweentwo adjacent pulses is less than a specified minimum spacing value, themethod includes deleting the 2nd pulse and making the pulse width forthe first pulse equal to the combined pulse width of the two originalpulse widths; and setting an FM value equal to the sum of the FM valuesof the two original pulse widths.
 16. The radio transceiver of claim 15further including circuitry and logic for combining each group of arraysinto a single group and for sorting the pulses within the single groupaccording to start time.
 17. The radio transceiver of claim 15 furtherincluding circuitry and logic for combining pulses again and, if thestart time between two adjacent pulses is less than the specifiedminimum spacing value, deleting the second pulse and keeping the firstpulse without adding the pulse widths.
 18. The radio transceiver ofclaim 15 further including circuitry and logic for adding pulse starttimes to a long pulse buffer for each pulse having a pulse width that isgreater than a specified minimum width value and less than a specifiedmaximum width value.
 19. The radio transceiver of claim 18 furtherincluding circuitry and logic for, if a difference in start timesbetween the newest pulse in the long pulse buffer and the oldest pulseis greater than a maximum window value, removing the oldest pulse andfor repeating this step until no more pulses are removed.
 20. The radiotransceiver of claim 19 further including circuitry and logic fordetermining that a radar has been detected if a number of pulses greaterthan a specified number of long pulses remain in the long pulse buffer.21. The radio transceiver of claim 19 further including circuitry andlogic for determining, if a radar signal is not detected because thenumber of pulses was not greater than the specified number of longpulses, performing radar pulse detection for traditional radar signals.22. The radio transceiver of claim 19 further including circuitry andlogic for detecting bin-5 category radar signals.